WinRT apps and Regional settings. The correct way to format dates and numbers based on the user's regional settings?

I'm having some problems in Windows 8 Metro apps (XAML & C#) regarding the user's regional settings. It seems that the apps won't respect user's regional settings, so even if your Windows 8 is set to display dates and times in Finnish format, the apps will still display them using US-formatting. But this is such a big problem that there must be something I'm missing?

To test this I started by creating a WPF-application. The application just prints out the CurrentCulture and the formatted DateTime.Now:

    private void Culture_Loaded_1(object sender, RoutedEventArgs e)
    {
        this.Culture.Text = System.Globalization.CultureInfo.CurrentCulture.DisplayName;
    }

    private void Date_Loaded_1(object sender, RoutedEventArgs e)
    {
        this.Date.Text = DateTime.Now.ToString();
    }

Here's my default regional settings:

When run, the app displayed the date in Finnish format:

Then I changed the regional settings to US:

And when the app was run again, the culture and formatting changed:

This is as I expected everything to work and this is also how I expected WinRT apps to work.

So as a next step, I created a WinRT (XAML & C#) app with the same code and reverted the regional settings back to Finnish. The problem:

Even when I've defined through regional settings that the formatting should be "Finnish", the WinRT app displays the datetime with US-formatting. I then modified the app's project file and made fi-FI the default language: